Stereo image display with switch function between horizontal display and vertical display

ABSTRACT

A stereo image display, switching between a first display direction and a second display direction, includes a polarized light module for providing a polarized light. A first light grating unit is implemented on the light path of the polarized light. When the first light grating unit is activated, the polarized light is modulated to output light in every two column; and when it is turned off, all the polarized light substantially passes. A second grating unit is implemented on the light path of the polarized light. When the second light grating unit is activated, the polarized light is modulated to output light in every two row; and when it is turned off, all the polarized light substantially passes. By the light passing the light grating units, an image displaying unit displays a first image at odd columns or rows and a second image at even columns or rows.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority benefit of Taiwan applicationserial no. 96151553, filed on Dec. 31, 2007. The entirety of theabove-mentioned patent application is hereby incorporated by referenceherein and made a part of specification.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a stereo image display technique, bywhich 2D or 3D image display may be switched in two display directions.

2. Description of Related Art

FIG. 1 is a cross-sectional view of a device provided by U.S. Pat. No.7,255,671,903. As shown in FIG. 1, a backlight plate 100 provides alight source to a parallax barrier 101, wherein the parallax barrier 101has transparent and opaque interlaced vertical strips for outputtinglight in interlaced strips, and in coordination with pixels within atransmissive display unit 102 and a position of human eyes. A first eyeof an observer may observe a first image, and a second eye may observe asecond image, such that a stereo display effect of 3D images separationfor the left eye and the right eye is then achieved. As shown in FIG. 1,the left eye may only observe the pixels in odd columns 01, 03, 05, 07and 09, and cannot observe the pixels in even columns; meanwhile, theright eye may only observe the pixels in the even columns 02, 04, 06, 08and 10, and cannot observe the pixels in the odd columns, so as to forma stereo image in a vision system.

FIG. 2 is a diagram illustrating another conventional technique. Astructural difference between the embodiments of FIG. 1 and FIG. 2 isthat positions of the parallax barrier 101 and the transmissive displayunit 102 are exchanged. In other words, in FIG. 1, the transmissivedisplay unit 102 is disposed on the same side of the backlight plate 100and the parallax barrier 101, while in FIG. 2, the transmissive displayunit 102 is disposed between the backlight plate 100 and the parallaxbarrier 101. The effect achieved by the embodiment of FIG. 2 is the sameto that of FIG. 1.

Another conventional technique is disclosed by U.S. Pat. No. 7,116,387.As shown in FIG. 3A and FIG. 3B, two pieces of microretarder plates 2and 3 with vertical interlaced 0 wavelength and λ/2 wavelengthretardation are provided, and based on relative horizontal movement ofthe two plates, two states of with parallax barrier and without parallaxbarrier may be switched, so as to switch between a 2D image display anda 3D image display. With coordination of the microretarder plate and apolarizing plate, switching between 2D and 3D image display then may beachieved based on movement of the microretarder plate. Moreover, atransmissive liquid crystal panel 1, two microretarder plates 2 and 3, apolarizing plate 4, a backlight module 5, two drivers 6 and 7 and acarrier 8 are illustrated in FIG. 3A and FIG. 3B.

A planar image output mode is illustrated in FIG. 3A, in which whenretardation patterns of the two microretarder plates 2 and 3 areoverlapped, polarized light may substantially pass through, and thedisplay unit 1 then displays a planar image. Moreover, a stereo imageoutput mode is illustrated in FIG. 3B, in which when allocation of theretardation patterns of the two microretarder plates 2 and 3 areinterlaced, striped intervals with 0 and λ/2 wavelength retardation aregenerated, such that the light is output in interlaced strips.Therefore, the display unit 1 then displays a stereo image, andaccordingly 2D and 3D display modes may be switched.

However, the conventional display structures may only have the 3Ddisplay effect in one display direction, for example the horizontaldirection, and therefore application thereof is limited.

SUMMARY OF THE INVENTION

The present invention is directed to a stereo image display device,which may be switched between a first display direction and a seconddisplay direction, and may have a 3D display effect in both displaydirections according to selection control of a user.

The present invention provides a stereo image display device including apolarized light source module, a first light grating unit, a secondlight grating unit and an image display unit. The polarized light sourcemodule is used for providing a polarized light. The first light gratingunit is disposed on a light path of the polarized light, wherein whenthe first light grating unit is activated, the polarized light ismodulated to form a first grating light source outputting light in everytwo columns in a first display direction, and when it is turned off, allthe polarized light substantially passes through. The second lightgrating unit is disposed on the light path of the polarized light, andwhen the second light grating unit is activated, the polarized light ismodulated to form a second grating light source outputting light inevery two rows in a second display direction, and when it is turned off,all the polarized light substantially passes through. When the firstlight grating unit generates the first grating light source, the secondlight grating unit is controlled to remain a state of the first gratinglight source. The image display unit displays a first image at oddcolumns or rows of pixels and a second image at even columns or rows ofpixels based on the light output from the light grating units.

The present invention provides another stereo image display deviceincluding a polarized light source module, a display unit, a first lightgrating unit and a second light grating unit. The polarized light sourcemodule is used for providing a polarized light source. The display unitis used for displaying a 2D or 3D first image corresponding to a firstdisplay direction, or displaying a 2D or 3D second image correspondingto a second display direction. The first light grating unit is disposedbetween the polarized light source module and the display unit, whereinthe first light grating unit includes a first liquid crystal plate formodulating the 3D first image in the first display directioncorresponding to a first state, or modulating the 2D first imagecorresponding to a second state. The second light grating unit isdisposed between the polarized light source module and the display unit,wherein the second light grating unit includes a second liquid crystalplate for modulating a polarization state of the polarized lightcorresponding to the 3D second image in the second display direction, ormodulating the polarization state of the polarized light correspondingto the 2D second image. When the first image of the first light gratingunit is the 3D image, the second light grating unit is controlled tomaintain a grating light source with a desired state.

The present invention provides still another stereo image display deviceincluding a polarized light source module, a first light grating unit, asecond light grating unit and an image display unit. The polarized lightsource is used for providing a polarized light source. The first lightgrating unit is disposed on a light path of the polarized light formodulating the polarized light to form a first light grating lightsource outputting light in every two columns. The second light gratingunit is disposed on a light path of the polarized light for modulatingthe polarized light to form a second light grating light sourceoutputting light in every two rows, wherein the second light gratinglight source may be turned off to allow outputting with the firstgrating light source. The image display unit is used for displaying afirst image at odd columns of pixels and a second image at even columnsof the pixels corresponding to the first light grating unit, anddisplaying a third image at odd rows of pixels and a fourth image ateven rows of the pixels corresponding to the second light grating unit.

In order to make the aforementioned and other objects, features andadvantages of the present invention comprehensible, a preferredembodiment accompanied with figures is described in detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram illustrating a conventional stereo imagedisplay mechanism applying a parallax barrier.

FIG. 2 is a schematic diagram illustrating another conventional stereoimage display mechanism.

FIGS. 3A-3B are schematic diagrams illustrating another conventionalstereo image display mechanism in which 2D and 3D image display may beswitched.

FIG. 4 is a structural cross-sectional view of a stereo image displaydevice according to an embodiment of the present invention.

FIG. 5 is a cross-sectional view of a stereo image display devicedisplaying in a horizontal direction according to an embodiment of thepresent invention.

FIG. 6 is a schematic diagram illustrating a strip structure of amicroretarder unit according to an embodiment of the present invention.

FIG. 7 is a cross-sectional view of a stereo image display devicedisplaying in a vertical direction according to an embodiment of thepresent invention.

FIG. 8 is a schematic diagram illustrating a 2D image display mechanismaccording to an embodiment of the present invention.

FIG. 9 is a schematic diagram illustrating a structure and function of ascattering liquid crystal unit according to an embodiment of the presentinvention.

FIGS. 10 and 11 are schematic diagrams in two viewing directions,illustrating another embodiment of the present invention, in which alight grating unit applies a design of a scattering liquid crystalmodule.

DESCRIPTION OF EMBODIMENTS

In application of display devices, disposition angles and methods of thedisplay devices may be different according to different requirements.For example, when a digital photo frame displays a horizontal or astraight photo, straight or horizontal disposition of the digital photoframe is generally determined. As to medical images, the medical imagescaptured by different capturing devices may be the horizontal orstraight images, and therefore disposition of the corresponding displaydevice may be switched to be horizontal or straight. However, as to apresent 3D display device, designed display directions are allhorizontal, and if the 3D display device is disposed straight, 3D effectthereof is then no more exist. According to a display technique providedby the present invention, a 3D screen may be adjusted according todifferent disposition methods, such that utilization of the 3D screen isrelatively not limited by the disposition method thereof. Moreover,according to the display technique of the present invention, a 2Ddisplay effect is compatible, and therefore such screen may be switchedamong planar image mode/vertical stereo image mode/horizontal stereoimage mode, and is convenient for users.

FIG. 4 is a structural cross-sectional view of a stereo image displaydevice displaying in a horizontal direction according to an embodimentof the present invention. Referring to FIG. 4, setting and mechanism forgenerating a 3D image in the horizontal display direction is firstdescribed. A polarized light source module 401 is applied for providinga light source which may provide light with a same polarizing feature.The polarized light passes through a light grating unit 402 to form astrip interlaced light, and then reaches an image display device 404 toform a first image at odd columns of pixels for sending to a first eyeof an observer, and form a second image at even columns of pixels forsending to a second eye of the observer, so as to form a stereo image.

The light grating unit 402 is composed of a scattering liquid crystalunit 402 a, a microretarder unit 402 b and a polarizing film 402 c. Thescattering liquid crystal unit 402 a functions as a polarized lightmodulation unit for modulating polarization of the polarized lightpassed through. The scattering liquid crystal unit 402 a has acontrollable transparent state and a scattering state. When thescattering liquid crystal unit 402 a is switched to the transparentstate, the polarized light with the original polarization is allowed topass through, and when scattering liquid crystal unit 402 a is switchedto the scattering state, the polarized light is then scattered, and theoriginal polarization of the polarized light is lost, such that nonpolarized light passes through the scattering liquid crystal unit 402 a.

If polarization direction of the polarized light source module is thesame to that of the polarizing film, when the generated polarized lightpasses through the strip region with λ/2 retardation of themicroretarder unit, the polarized light is rotated for 90 degrees, andcannot pass through the polarizing film 402 c, such that an opaque areais formed. Meanwhile, when the polarized light passes through the stripregion with 0 retardation, the polarized light may pass through thepolarizing film due to same phases thereof, such that a transparent areais formed, and the light is then output in strips in every two columns,so as to form the stereo image. The same polarized light generated fromthe polarized light source module 401 enters the light grating unit 402,and now the scattering liquid crystal unit 402 a is controlled toscatter the polarization of the input light to form the non-polarizedlight. Base on phase distribution of the microretarder unit, suchnon-polarized light may have no effective optical function in overview.Therefore, the light grating unit 402 does not form a parallax grating,which is referring to as a turned off state. Otherwise, the lightgrating unit 402 is in a turned on state and forms the parallax grating.When the light grating unit 402 is turned off, a mono polarized light isallowed to pass through the polarizing film 402 c, and after processingby the image display device, the mono polarized light enters eyes of theobserver, and now the observer may view a planar image.

Next, based on function of the microretarder unit of the light gratingunit, an embodiment is provided, by which the 3D image may be displayedin two display directions. FIG. 5 is a cross-sectional view of a stereoimage display device displaying in a horizontal direction according toan embodiment of the present invention. Referring to FIG. 5, arrowdirections represent polarization directions of the light. The stereoimage display device may include a polarized light source module 500, afirst light grating unit (502+504+506), a second grating unit(508+510+512) and an image display unit. The polarized light sourcemodule 500 is used for providing a polarized light. The first lightgrating unit is disposed on a light path of the polarized light, whereinwhen the first light grating unit is activated, the polarized light ismodulated to form a first grating light source outputting light in everytwo columns in a first display direction; and when it is turned off, allthe polarized light substantially passes through. The second lightgrating unit is disposed on the light path of the polarized light,wherein when the second light grating unit is activated, the polarizedlight is modulated to form a second grating light source outputtinglight in every two rows in a second display direction, and when it isturned off, all the polarized light substantially passes through. Asshown in FIG. 5, the second light grating unit (508+510+512) is turnedoff. The image display unit may be a transmissive display unit 514,which may display a first image at odd columns or rows of pixels and asecond image at even columns or rows of pixels based on the light outputfrom the light grating units, wherein the image displayed in the columnsis the horizontal image displayed when the display device is disposedhorizontally, and the image displayed in the rows is the straight imagedisplayed when the display device is disposed straight.

For example, when the 3D image is displayed in the horizontal direction,the polarized light source module 500 provides a light source which mayprovides 0 degree polarized light as shown in FIG. 5. In the followingdescription, polarized light with an initial state of 0 degree is takenas an example, though the present embodiment is not limited thereto, thepolarized light with the initial state of 90 degrees may also beapplied. After the polarized light passes through an activated liquidcrystal unit 502 with 45 degree polarization rotation, the polarizedlight is polarized to 45 degrees and then transmitted to a microretarderunit 504 with a fast axis (or a slow axis) thereof disposing in 0degree. The microretarder unit 504 has different retardations in thehorizontal direction, i.e. has vertical strip interlaced patterns with 0wavelength retardation and λ/2 wavelength retardation as shown in FIG.6. After the 45 degree polarized light passes through the microretarderunit 504, the odd strips are changed to 135 degree polarized light, andthe even strips remain 45 degree polarized light. Thereafter, thepolarized light is transmitted to a 45 degree polarizing film 506,wherein the 135 degree polarized light cannot pass through thepolarizing film 506, so as to form a grating light source. Polarizedlight emitted from such grating light source passes through a secondturned off liquid crystal unit 508 with 45 degree polarization, andpolarization state thereof is not changed.

Next, since direction of the fast axis of a microretarder unit 510 has45 degrees difference with that of the microretarder unit 504, which isdisposed in 45 degrees as that shown in FIG. 5, polarization state ofthe polarized light passed through the microretarder unit 510 is notchanged and maintains 45 degrees. However, since a polarizing film 512is disposed in 90 degrees, a part of the 45 degree polarized light maystill passes through the polarizing film 512. Light emitted from thegrating light source maintains a same grating state and is transmittedto the liquid crystal image display unit. Therefore, the first imagedisplayed at odd columns of pixels is transmitted to the first eye ofthe observer, and the second image displayed at even columns of pixelsis transmitted to the second eye of the observer, so as to form thestereo image in the horizontal direction.

FIG. 6 is a schematic diagram illustrating a strip structure of amicroretarder unit according to an embodiment of the present invention.The microretarder unit 506 has a plurality of interlaced first stripareas 504 a and a plurality of interlaced second strip areas 504 b.Wherein, the first area 504 a has a stretching structure forimplementing the λ/2 retardation, and the second area 504 b does nothave the stretching structure, and therefore retardation difference ofthe first area 504 a and the second area 504 b is λ/2. Certainly, thefirst area 504 a and the second area 504 b may be exchanged according toan actual requirement. The polarization of light passes through thefirst area 504 a rotate for 90 degrees for being perpendicular to thepolarization of the second area 504 b. Actually, as long as a totalretardation difference between the first area and the second area of themicroretarder unit 504 reaches λ/2, the structure is applicable. Thefirst area 504 a and the second area 504 b may simultaneously have theretardant structure.

FIG. 7 is a cross-sectional view of a stereo image display devicedisplaying in a vertical direction according to an embodiment of thepresent invention. The structure shown in FIG. 7 is the same to thatshown in FIG. 5, though FIG. 7 is a cross-sectional view in the verticaldirection for explaining the display mechanism when the display deviceis disposed straight. Referring to FIG. 7, the polarized light sourcemodule 500 provides a light source which may provides 0 degree polarizedlight, though the 0 degree polarized light is perpendicular to thedrawing paper. After passing through the turned off first liquid crystalunit 502 with 45 degree polarization rotation, the polarized lightmaintains the 0 degree polarization state, and then the polarized lightpasses through the microretarder unit 504 with the 0 degree retardationand the λ/2 retardation and the polarizing film 506 disposed in 45degrees. In FIG. 7, the fast axis of the microretarder unit 504 isdisposed in 0 degree, and therefore the polarized light is maintainedwith the 0 degree polarization state. The polarized light is polarizedto 45 degrees after passing through the polarizing film 506, and thenthe polarized light is again polarized to 90 degrees after passingthrough the activated second liquid crystal unit 508 with 45 degreepolarization rotation. Thereafter, the polarized light is transmitted tothe microretarder unit 510, wherein the microretarder unit 510 hasdifferent retardations in the vertical direction, i.e. has horizontalstrip interlaced patterns with 0 wavelength retardation and λ/2wavelength retardation. The 90 degree polarized light maintains the 90degree polarization after passing through the strips with 0 wavelengthretardation and reaches the polarizing film 512 disposed in 90 degrees.Thereafter, the polarized light continually passes through thepolarizing film 512 and reaches the transmissive display unit 514.Moreover, the polarized light passing through the strips with λ/2wavelength retardation again rotate 90 degrees to form the 0 degreepolarized light. Since there are 90 degree phase difference between the0 degree polarized light and the polarizing film 512, the 0 degreepolarized light cannot pass through the polarizing film 512, such that agrating light source is formed. Therefore, the first image displayed atodd rows of pixels is transmitted to the first eye of the observer, andthe second image displayed at even rows of pixels is transmitted to thesecond eye of the observer, so as to form the stereo image in thevertical direction.

The aforementioned mechanism is for the 3D image display, however, ifoperation mechanism of the light grating unit is different, displaymechanism thereof is also different, so as to achieve the grating lightsource effect. In the following content, switching of the 2D imagedisplay mechanism is first described. FIG. 8 is a schematic diagramillustrating a 2D image display mechanism according to an embodiment ofthe present invention. Referring to FIG. 8, 2D image display may beachieved with the same components shown in FIG. 5 under a differentoperation. The polarized light source module 500 provides a light sourcewhich may provides 0 degree polarized light. Now, the liquid crystalunit 502 with 45 degree polarization rotation is turned off, andtherefore the polarized light is maintained with 0 degree polarization.Next, the 0 degree polarized light passes through the microretarder unit504, and since the fast axis thereof is disposed in 0 degree, thepolarized light is maintained to the 0 degree polarization state. Sincepolarization direction of the incident light is also 0 degree, an anglebetween the direction of the fast axis of the microretarder unit 504 andthe polarization direction of the incident light is also 0 degree. Themicroretarder unit 504 is used for double rotating the angle, and sincethe angle is 0, there is no actual rotation thereof. Therefore, thepolarization direction of the polarized light after passing through themicroretarder unit 504 is still maintained to 0 degree. Next, afterpassing through the 45 degree polarizing film 506, the light ispolarized for 45 degrees. Such 45 degree polarized light maintains thesame polarization state after passing through the turned off secondliquid crystal unit 508 with 45 degree polarization rotation. Next, the45 degree polarized light passes through the microretarder unit 510, andsince the fast axis of the microretarder 510 is disposed in 45 degrees,polarization state of the polarized light is still maintained to 45degrees. Thereafter, the polarized light passes through the 90 degreepolarizing film 512 and forms the 90 degree polarized light. Besides thepolarized light is polarized to 90 degrees, a planar light source ismaintained to be provided to the liquid crystal image display unit, andtherefore the image is displayed in the 2D mode.

In the aforementioned light grating unit, by transforming of opticalpolarization state under function of the microretarder units 504 and510, switch function of displaying the 3D and the 2D images between twodisplay directions may be achieved. However, structure of the lightgrating unit and control mechanism thereof is not limited to theaforementioned embodiment, for example, the liquid crystal units 502 or508 with 45 degree polarization rotation of the light grating unit mayalso be substituted by the scattering liquid crystal unit of FIG. 4. The45 degree polarizing film 506 may also be substituted by the 135 degreepolarizing film. Moreover, if the initial light polarization state is 90degrees, by controlling the light grating unit, the grating light sourcerequired for 3D displaying may also be achieved.

FIG. 9 is a schematic diagram illustrating a structure and function of ascattering liquid crystal unit according to an embodiment of the presentinvention. Referring to FIG. 9, a scattering liquid crystal module 901is also a polarized light modulation unit, which is used for modulatingpolarization of the passing through polarized light. As theaforementioned description of FIG. 4, the scattering liquid crystal unithas the controllable transparent state and the scattering state. Aliquid crystal layer 10001 d is hold by an upper transparent substrateand a lower transparent substrate. When the scattering liquid crystalunit is set to the transparent state, polarization direction of anincident light 1001 a passed through the scattering liquid crystalmodule 901 is not changed. If the incident light is the polarized light1001 a, polarization feature thereof is maintained. When the scatteringliquid crystal unit 1001 d is switched to the scattering state,polarization direction of the incident polarized light 1001 a is thenscattered, and a non polarized light 1001 e is then output to form ageneral light source. The scattering liquid crystal module 901 may beutilized with the microretarder unit and the polarizing film to generatethe grating light source.

FIGS. 10 and 11 are schematic diagrams in two viewing directions,illustrating another embodiment of the present invention, in which alight grating unit applies a design of a scattering liquid crystalmodule. FIG. 10 is another embodiment at the horizontal display mode.For example, a polarized light source module 600 generates a polarizedlight with 0 degree polarization. The polarized light may pass through ascattering liquid crystal module 602 and maintain the polarization statethereof when the scattering liquid crystal module is in the transparentstate.

Next, the fast axis (or the slow axis) is disposed at the microretarderunit 604 at 45 degrees. The microretarder unit 604 has different phasedifferent at the horizontal direction. In other words, it has thepattern for the vertical strips with 0 phase and λ/2 phase inalternative change. After the 0-degree polarization light passes themicroretarder unit 604, the odd light beam become the 90-degreepolarization light and the even light beams remain at 0-degreepolarization. Then, after passing the 0-degree polarization film 606,the light beam with 90 degree polarization cannot pass. As a result, alight source with grating is formed. This light source passes the secondliquid crystal unit 608 at off state, and the polarization stateremains.

Next, the light source passes the second microretarder unit 610, whichhas the fast axis at o degree. Since the polarization direction of themicroretarder unit 610 different from the microretarder unit 604 by 45degrees, as shown in FIG. 11, the polarization state of the light sourceremains at 0 degree after passing the microretarder unit 610. However,since the polarizing film 612 is at the 45 degrees, a portion of thelight for the light at 0 degree polarization can still pass thepolarizing film 612. The grating effect of the light source can stillremain the same to enter the transmissive display unit 614. In thissituation, the pixels at odd columns display the first image to one eyeof the observer; the pixels at even columns display the second image toanother eye of the observer, so as to form a stereo image at thehorizontal direction.

In FIG. 11, when the same apparatus is operated in vertical displaymode, the display mechanism is shown. The polarized light source module600 generates 0 degree polarization light in the direction perpendicularto the drawing sheet due to viewing from the side. The scattering liquidcrystal module 602 is at the scattering state, so that the polarizationeffect disappears. Even though the microretarder unit 604 has the stripswith 0 phase and λ/2 phase in alternative change, the microretarder unit604 does not produce polarizing effect. Then, the polarizing film 606polarizes the passing light into the 0 degree polarization state. Thesecond liquid crystal unit 608 is at on state and thereby rotate thepolarization direction by 45 degrees at 135 degrees. The strip patternof the second microretarder unit 610 in this cross-section is seen. Thestrip with shade is the strip having λ/2 phase and rotates thepolarization direction by 90 degrees. The strips of the microretarderunit 610 with white are at 0 phase and let the light pass withoutchange. The 45 degree polarizing film 612 filters the light with thepolarization direction at 135 degrees, and produces the grating lightsource. In this situation, the pixels at odd rows display the firstimage to one eye of the observer; the pixels at even rows display thesecond image to another eye of the observer, so as to form a stereoimage at the vertical direction.

In other words, in the present invention, by applying two light gratingunits, the grating light source may be generated in two displaydirections, and the light source for 2D image display may also beswitched.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the structure of the presentinvention without departing from the scope or spirit of the invention.In view of the foregoing, it is intended that the present inventioncover modifications and variations of this invention provided they fallwithin the scope of the following claims and their equivalents.

1. A stereo image display device, having a switch function between afirst display direction and a second display direction, comprising: apolarized light source module, for providing a polarized light; a firstlight grating unit, disposed on a light path of the polarized light,wherein when the first light grating unit is activated, the polarizedlight is modulated to form a first grating light source for outputtinglight in every two columns in the first display direction, and when thefirst light grating unit is turned off, all the polarized lightsubstantially passes through; a second light grating unit, disposed onthe light path of the polarized light, wherein when the second lightgrating unit is activated, the polarized light is modulated to form asecond grating light source for outputting light in every two rows inthe second display direction, and when the second light grating unit isturned off, all the polarized light substantially passes through, andwhen the first light grating unit generates the first grating lightsource, the second light grating unit is controlled to maintain a stateof the first grating light source; and an image display unit, displayinga first image at odd columns or rows of pixels and a second image ateven columns or rows of pixels based on a light output from the lightgrating units.
 2. The stereo image display device as claimed in claim 1,wherein the first light grating unit comprises: a first microretarderunit, having a first phase modulation material and a second phasemodulation material respectively arranged in every two columns anddistributed in the first display direction, so as to respectivelymodulate a phase of the polarized light for outputting; and a firstpolarizing film, allowing a polarized light with a predeterminedpolarization state to pass through, wherein the second light gratingunit comprises: a second microretarder unit, having a third phasemodulation material and a fourth phase modulation material respectivelyarranged in every two columns and distributed in the second displaydirection, so as to respectively modulate phase of the polarized lightfor outputting; and a second polarizing film, allowing a polarized lightwith a predetermined polarization state to pass through.
 3. The stereoimage display device as claimed in claim 2, wherein the first lightgrating unit further comprises: a first polarized light modulation unit,disposed between the polarized light source module and the firstpolarizing film, being switched between a first state and a secondstate, wherein when the first polarized light modulation unit isswitched to the first state, the polarized light is allowed to passthrough while maintaining an original polarization feature thereof; andwhen the first polarized light modulation unit is switched to the secondstate, a polarization state of the polarized light is transformed, andthe transformed polarized light is then output; and the second lightgrating unit further comprises: a second polarized light modulationunit, disposed between the polarized light source module and the secondpolarizing film, being switched between a first state and a secondstate, wherein when the second polarized light modulation unit isswitched to the first state, the polarized light is allowed to passthrough while maintaining an original polarization feature thereof; andwhen the second polarized light modulation unit is switched to thesecond state, a polarization state of the polarized light istransformed, and the transformed polarized light is then output.
 4. Thestereo image display device as claimed in claim 3, wherein the firstpolarized light modulation unit is a scattering liquid crystal unitcapable of being switched between a transparent state and a scatteringstate: (a) when the scattering liquid crystal unit is switched to thetransparent state, the polarized light is allowed to pass through whilemaintaining an original polarization feature; and (b) when thescattering liquid crystal unit is switched to the scattering state, thepolarized light is scattered and transformed to a non-polarized lightfor outputting.
 5. The stereo image display device as claimed in claim4, wherein a position of the scattering liquid crystal unit is closer tothe polarizing film than the microretarder unit.
 6. The stereo imagedisplay device as claimed in claim 4, wherein a position of thescattering liquid crystal unit is farther away from the polarizing filmthan the microretarder unit.
 7. The stereo image display device asclaimed in claim 2, wherein an angle difference between two fast axes ofthe first microretarder unit and the second microretarder unit is 45degrees.
 8. The stereo image display device as claimed in claim 2,wherein the first phase modulation material and the second phasemodulation material of the first light grating unit are disposed to havea retardation difference there between substantially equal to 90degrees; and the third phase modulation material and the fourth phasemodulation material of the second light grating unit are disposed tohave a retardation difference substantially equal to 90 degrees.
 9. Thestereo image display device as claimed in claim 2, wherein at least oneof the first light grating unit and the second light grating unitcomprises: a uniform microretarder unit, with a stretching directionsubstantially perpendicular to that of the microretarder unit, anddisposed between the polarized light source module and the microretarderunit.
 10. The stereo image display device as claimed in claim 1, whereinthe first display direction is substantially perpendicular to the seconddisplay direction.
 11. The stereo image display device as claimed inclaim 1, wherein the first light grating unit comprises: a first liquidcrystal unit with 45 degree polarization rotation, in which apolarization state of a passing through light is not changed when thefirst liquid crystal unit with 45 degree polarization rotation is turnedoff, and the polarization state of the passing through light ispolarized for 45 degrees when the first liquid crystal unit with 45degree polarization rotation is activated; a first microretarder unit,having a first phase modulation material and a second phase modulationmaterial respectively arranged in every two columns and retardationdifference is half wavelength, and distributed in the first displaydirection; and a 45 degree polarizing film, wherein the second lightgrating unit comprises: a second liquid crystal unit with 45 degreepolarization rotation, in which a polarization state of a passingthrough light is not changed when the second liquid crystal unit with 45degree polarization rotation is turned off, and the polarization stateof the passing through light is polarized for 45 degrees when the secondliquid crystal unit with 45 degree polarization rotation is activated; asecond microretarder unit, having a third phase modulation material anda fourth phase modulation material respectively arranged in every twocolumns and retardation difference is half wavelength, and distributedin the second display direction; and a 90 degree polarizing film.
 12. Adual-mode image display device, comprising: a polarized light sourcemodule, for providing a polarized light source; a display unit, fordisplaying a 2D first image or a 3D first image corresponding to a firstdisplay direction, or displaying a 2D second image or a 3D second imagecorresponding to a second display direction; a first light grating unitdisposed between the polarized light source module and the display unit,wherein the first light grating unit includes a first liquid crystalplate displaying the 3D first image in the first display directioncorresponding to a first state, or displaying the 2D first imagecorresponding to a second state; a second light grating unit disposedbetween the polarized light source module and the display unit, whereinthe second light grating unit includes a second liquid crystal platedisplaying the 3D second image in the second display directioncorresponding to a first state, or displaying the 2D second imagecorresponding to a second state, and when the first light grating unitis operated for the 3D first image, the second light grating unit iscontrolled to maintain a light grating light source with a desiredstate.
 13. The dual-mode image display device as claimed in claim 12,wherein the polarized light source module is a polarized light sourcemodule of a whole structure, in which the polarized light source modulewith the polarization state is obtained by applying a polarizing film.14. The dual-mode image display device as claimed in claim 12, wherein apolarizing film is disposed at a side where the first light grating unitand the second light grating unit face to the display unit.
 15. Thedual-mode image display device as claimed in claim 12, wherein the firstand the second liquid crystal plates are in a fixed position withoutmoving.
 16. The dual-mode image display device as claimed in claim 12,wherein the first light grating unit and the second light grating unitrespectively further comprises: a microretarder unit, having a firstarea and a second area, wherein when the first liquid crystal plate orthe second liquid crystal plate is in the first state, the first areaand the second area form a parallax grating, and when the first liquidcrystal plate or the second liquid crystal plate is in the second state,the first area and the second area do not form the parallax grating. 17.The dual-mode image display device as claimed in claim 16, wherein thefirst area and the second area of the microretarder unit have 90 degreeretardation difference based on an incident angle of the polarizedlight, and polarization states of the first and second areas areperpendicular to each other.
 18. The dual-mode image display device asclaimed in claim 16, wherein an angle difference between two fast axesof the two microretarder units of the first light grating unit and thesecond light grating unit is 45 degrees.
 19. The dual-mode image displaydevice as claimed in claim 12, wherein the first state of the firstliquid crystal plate of the first grating unit or the second liquidcrystal plate of the second grating unit is the transparent state, andthe second state thereof is to rotate an incident polarization state for45 degrees.
 20. A stereo image display device, comprising: a polarizedlight source module, for providing a polarized light; a first lightgrating unit, disposed on a light path of the polarized light, formodulating the polarized light to form a first grating light sourceoutputting light in every two columns; a second light grating unit,disposed on the light path of the polarized light, located farther awayfrom the polarized light source module than the first light gratingunit, for modulating the polarized light to form a second grating lightsource outputting light in every two rows, and for turning off thesecond light grating light source to allow outputting of the first lightgrating light source; and an image display unit for displaying a firstimage at odd columns of pixels and a second image at even columns of thepixels corresponding to the first light grating unit, and displaying athird image at odd rows of the pixels and a fourth image at even rows ofthe pixels corresponding to the second light grating unit.
 21. Thestereo image display device as claimed in claim 20, wherein lightoutputting of the first light grating unit and the second light unit inevery two columns/rows are turned off, so as to switch to a 2D imagedisplay.
 22. The stereo image display device as claimed in claim 20,wherein the first light grating unit and the second light grating unitrespectively comprises a microretarder unit with strip directionsthereof perpendicular to each other, and an angle difference betweenfast axes thereof is 45 degrees.
 23. The stereo image display device asclaimed in claim 22, wherein at least one of the first grating unit andthe second grating unit comprises: a uniform microretarder unit, with astretching direction substantially perpendicular to that of themicroretarder unit, and disposed between the polarized light sourcemodule and the microretarder unit.